The invention relates generally to disk based data storage systems and, more particularly, to filter structures for use therein.
A disk drive is a data storage device that stores data in concentric tracks on a disk shaped medium. Data is read from the medium by spinning the medium about a central axis while positioning a transducer near a desired track of the medium to sense the data. The transducer provides an electrical signal representative of the sensed data to data processing circuitry within the disk drive which converts the electrical signal to a format that is recognizable by an attached host unit. The converted data signal is then delivered to the host unit for use thereby. Disk drives can store data in any of a number of different forms, such as magnetic data storage and optical data storage.
Disk drive units are normally enclosed within a housing to protect the workings of the drive from the exterior environment. As can be appreciated, any undesirable substances that exist within the disk drive housing can have a deleterious effect on the operation thereof. For example, in a magnetic disk drive, particles and volatile gases within the drive housing can result in performance problems such as stiction between the magnetic transducer and the disk, transducer crashes, and thermal asperities. To reduce such occurrences, the level of airborne particles and gases within the disk drive should be kept low.
Therefore, there is a need for a filtering structure to reduce the levels of undesired substances within the housing of a disk drive.
The present invention relates to an integrated filter structure for use in a disk drive. The integrated filter includes a recirculation filter, a breather filter, and a chemical filter all housed within a single support structure. The recirculation filter is operative for reducing the level of airborne particles circulating within the disk drive housing. These airborne particles can include, for example, wear particles generated by friction between the transducer and the disk medium of the disk drive during start and stop operations. The breather filter is operative for trapping solid particles entering the disk drive housing from an exterior environment through a breather port in the housing. Likewise, the chemical filter is operative for absorbing undesirable gases entering the disk drive from the exterior environment. The integrated filter can also include a diffusion path for providing condensation of vapors within air entering the disk drive housing through the breather port. During disk drive manufacture, the integrated filter is inserted into the disk drive housing as a single unit, thereby reducing the number of steps required to assemble the drive.
In one embodiment of the invention, the filter elements are housed within a frame having at least two cavities. The first cavity carries the recirculation filter and the second cavity carries the chemical and breather filters. The first cavity is located above the second cavity and includes two sidewalls having inclined upper edges. The recirculation filter is attached to the upper edges of the two sidewalls forming an enclosed space within the first cavity having a single input port for receiving circulating air. Because the upper edges of the sidewalls are inclined, a relatively large recirculation filter input surface is achieved. The second cavity of the filter frame includes first and second fluid ports, the first port for communicating with an environment external to the disk drive housing and the second port for communicating with the internal chamber of the disk drive. In this manner, air flow from the exterior environment into the disk drive housing occurs through the chemical and breather filters carried by the second cavity.
In another embodiment, a frame having a single cavity is provided. The chemical filter, the breather filter, and the optional diffusion channel are disposed within the single cavity. In addition, the recirculation of the cavity. Air currents impinging upon the recirculation filter create a low-pressure condition within the cavity that draws air into the disk drive from the exterior environment through the chemical and breather filters the diffusion channel.
Preferably, the support structure of the integrated filter is shaped to conform to a recessed pocket within the baseplate. During assembly of the disk drive, the integrated filter is inserted into the pocket of the baseplate which thereafter holds the integrated filter in a fixed position. The baseplate can also include a sloped recessed portion leading to the pocket area for creating a low pressure region that channels circulating air in a lower portion of the disk drive chamber into the recirculation filter. A second recessed portion can also be provided in the baseplate on another side of the pocket to provide a low pressure region for facilitating air flow through the breather and chemical filters. After the integrated filter has been inserted into the pocket of the baseplate, the second port of the second cavity communicates directly with the second recessed portion of the baseplate.
In one embodiment, a dam structure is provided on a disk drive cover plate to increase the filtering efficiency of the integrated filter. In a typical disk drive, a gap is formed between a lower surface of the cover plate and the upper surface of the uppermost disk in the drive. The dam structure of the invention adds a dropped portion to the lower surface of the cover plate in an area near the location of the integrated filter, thus reducing the height of the gap between the cover plate and the upper disk and increasing the air pressure in this region. The increased air pressure is operative for channeling circulating air currents from the region between the upper disk and the cover plate into the recirculation filter.